The overall objective of this proposal is to identify genes that influence susceptibility to cardiovascular disease through their influence on levels of coronary artery calcification (CAC). The presence and quantity of CAC predicts risk of future CVD events and levels of CAC are highly heritable. This proposal takes advantage of two large cohorts of individuals who have been phenotyped for CAC using EBCT technology and recent advances in genomics that make feasible the identification of disease susceptibility genes through genome-wide association (GWA) approaches. We hypothesize that genes influencing variation in CAC will be readily identified through GWA analysis with densely spaced SNPs. To test this hypothesis, we will carry out a 2-stage design in which we will first screen 800 Amish subjects using a GWA scan (Stage I), and then genotype associated SNPs in a second (Stage II) population of European Caucasian ancestry individuals from Rochester, MN from the Epidemiology of Coronary Artery Calcification Study. The Amish are a particular advantageous population to carry out such studies because of their common genetic ancestry and homogenous lifestyle. Through previous work, we have measured CAC in 800 Amish adults, in whom we are currently genotyping 500K Affymetrix SNP chips as part of other studies. In Specific Aim 1, we will genotype the remaining 300 subjects and carry out a GWA analysis of CAC. In Specific 2, we will identify the 1,750 most significantly associated SNPs from Stage 1 (representing 0.35% of the total number of SNPs tested) and will genotype these, as well as two flanking SNPs for each, in 900 subjects from the ECAC Study. Following these analyses, we will (as Specific Aim 3), prioritize the most compelling positional candidate genes and perform exhaustive analysis for sequence variation followed by association analysis to identify the most likely causative SNPs/haplotypes. Discovery of CAC susceptibility genes will provide: (i) critical insights into molecular mechanisms;(ii) new targets for therapy;(ii) blood tests for early detection of at risk persons so that preventive interventions can be instituted. This will impact substantially on mortality, quality of life, and health care costs for millions of middle-aged and elderly Americans.